Tris-dithiocarbamate Functionalized Silver Nanoparticles as a Selective Colorimetric Sensor for Detection of Melamine in Milk

The aim of this study was to develop a cheap, selective, sensitive and practical method for detecting melamine in raw milk samples. Tris-dithiocarbamate was prepared by the reaction of 2-amino-2-hydroxy-propane-1,3-diol (tris base), as a cheap and available base, with carbon disulfide. Due to the presence of the dithiocarbamate together with the hydroxyl functional groups, there is a strong tendency to interact with melamine. Electron donor-electron acceptor interaction between melamine and tris-dithiocarbamate on the surface of silver nanoparticles leads to the aggregation of silver nanoparticles, which causes the absorption wavelength of nanoparticles to shift to higher wavelengths and the color of the solution changes from bright yellow to red. This color change has been recorded and measured using ultraviolet-visible (UV-Vis) spectroscopy. This method can be used to quickly measure the small amount of melamine in pasteurized milk samples. The detection limit of the method is 0.7 µM, and the sensor is completely selective towards melamine. The linear range of the method is 2 µM -12 µM, which is competitive with many similar methods reported.